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<h2><a name="SECTION0019620000000000000000"></a><a name="asynchat-example"></a>
<br>
17.6.2 asynchat Example 
</h2>

<p>
The following partial example shows how HTTP requests can be read with
<tt class="class">async_chat</tt>. A web server might create an <tt class="class">http_request_handler</tt> object for
each incoming client connection. Notice that initially the
channel terminator is set to match the blank line at the end of the HTTP
headers, and a flag indicates that the headers are being read.

<p>
Once the headers have been read, if the request is of type POST
(indicating that further data are present in the input stream) then the
<code>Content-Length:</code> header is used to set a numeric terminator to
read the right amount of data from the channel.

<p>
The <tt class="method">handle_request()</tt> method is called once all relevant input
has been marshalled, after setting the channel terminator to <code>None</code>
to ensure that any extraneous data sent by the web client are ignored.

<p>
<div class="verbatim"><pre>
class http_request_handler(asynchat.async_chat):

    def __init__(self, conn, addr, sessions, log):
        asynchat.async_chat.__init__(self, conn=conn)
        self.addr = addr
        self.sessions = sessions
        self.ibuffer = []
        self.obuffer = ""
        self.set_terminator("\r\n\r\n")
        self.reading_headers = True
        self.handling = False
        self.cgi_data = None
        self.log = log

    def collect_incoming_data(self, data):
        """Buffer the data"""
        self.ibuffer.append(data)

    def found_terminator(self):
        if self.reading_headers:
            self.reading_headers = False
            self.parse_headers("".join(self.ibuffer))
            self.ibuffer = []
            if self.op.upper() == "POST":
                clen = self.headers.getheader("content-length")
                self.set_terminator(int(clen))
            else:
                self.handling = True
                self.set_terminator(None)
                self.handle_request()
        elif not self.handling:
            self.set_terminator(None) # browsers sometimes over-send
            self.cgi_data = parse(self.headers, "".join(self.ibuffer))
            self.handling = True
            self.ibuffer = []
            self.handle_request()
</pre></div>

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<span class="release-info">Release 2.5.1, documentation updated on 18th April, 2007.</span>
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